This invention relates to a method of producing a supported catalyst component, the catalyst component produced according to the method, to an olefin polymerization supported catalyst composition, and to an olefin polymerization process using such a supported catalyst.
Supported catalysts of the Ziegler or Ziegler-Natta type can be used in the polymerization of olefins in various types of polymerization reaction systems, including high pressure, solution, slurry, and gas phase processes. Different techniques are known for producing supported catalysts. In each of the known techniques the reactive catalytic metal (e.g., titanium) is typically added after preparation of the support. This support is typically a magnesium halide or alkoxide species, or a silica support onto which a magnesium halide or alkoxide is deposited.
For example, U.S. Pat. No. 4,526,943 discloses an olefin polymerization catalyst prepared by the reaction of a hydrocarbon soluble organomagnesium compound with a trialkylaluminum reagent and an aliphatic alcohol to generate a soluble magnesium alkoxide precursor to which a transition metal compound (typically a titanium compound) is added. U.S. Pat. No. 4,560,733 teaches the use of a catalyst system having a titanium coating component made from a milled blend of two different supports, each support being treated with a dihyrocarboxylmagnesium compound, and a halogenated tetravalent titanium compound.
U.S. Pat. Nos. 4,672,096 and 4,670,413 disclose contacting a magnesium compound and the carrier with a transition metal (e.g., titanium or vanadium) compound to produce a supported solid catalyst composition.
With each of these methods the support treated with the organomagnesium halide compound is subsequently treated by the addition of the polymerization active transition metal. These procedures can lead to a less than uniform distribution of polymerization active metal on the catalytic support and can involve difficult handling procedures such as refluxing the catalyst precursors in neat or concentrated solutions of the transition metal reagent until sufficient metal absorption has been achieved. Furthermore, by adding the active metal to the precursor after the precursor is formed, in order to obtain a sufficient quantity of catalytic metal, the active metal salt must often be added in excess requiring the additional step of eliminating the excess afterwards. Failure to remove the excess metal salt can produce soluble polymerization active metal centers that adversely affect slurry and gas phase polymerization processes, i.e., formation of skins or agglomerates.
Accordingly, it is the object of the present invention to overcome these problems and disadvantages by providing an active polymerization catalyst and one that does not require the subsequent addition of the polymerization active transition metal. Moreover, the additional object of the present invention is to eliminate handling and excessive transition metal reagent usage associated with the preparation of the typical Ziegler-Natta catalysts. Furthermore, the present invention converts normally inactive transition metal centers into centers capable of preparing narrow molecular weight distribution olefins such as ethylene or other xcex1-olefins. The present invention also achieves a catalyst that is displays excellent hydrogen response and is capable of producing a range of moleular weight polymers from ultra high molecular weight (zero melt flow) polyethylene to low molecular weight (high melt flow) polyethylene.
In accordance with one aspect of the present invention, there is provided novel compositions of matter which are useful for polymerization of olefins by providing a catalyst composition that does not require the additional treatment with the polymerization active transition metal.
Also provided in accordance with this invention are methods for making the novel compositions and methods of using the compositions for polymerization of olefins. In its broadest form, the method of producing the supported catalytic composition of the present invention comprises treating an inorganic support (e.g., gels, co-gel, tergels) which has incorporated therein a Groups 3-10 transition metal from the Periodic Table with a metal alkylating reagent wherein the reaction product is then treated with a halogenating reagent. The resultant reaction product is, optionally, recovered and available for use in conjunction with the activating co-catalyst (a.k.a an activator) for the polymerization of polyolefins.
The present invention is directed to a novel method of making active polymerization catalyst compositions and the novel composition provided therefrom. The method of the present invention provides that a supported catalyst component is obtained by:
1) treating a support, preferably calcined and preferably a gel, co-gel or tergel and mixtures thereof, containing at least one Group 3-10 transition metal, preferably an oxide, with an alkylating reagent;
2) treating the reaction product from step one with a halogenating reagent; and, optionally,
3) recovering the reaction product from step 2.
The resulting catalyst is suitable for homo-polymerizing and copolymerizing olefinic monomers and co-monomers, particularly, ethylene and other xcex1-olefins, e.g., propylene, 1-butene, 1-hexene.
The catalysts produced according to the present invention are described below in terms of the manner in which they are made.
The Metal Containing Support Material
The metal containing support can be purchased from suppliers or prepared using known techniques wherein the metal is uniformly distributed throughout the support""s structure. For example, U.S. Pat. No. 3,887,494 teaches one method of preparing a SiO2xe2x80x94TiO2 cogel. Any inorganic or inorganic oxide support material containing a metal from the Group 3-10 transitional metals from the Periodic Table can be used in this invention upon mixing with suitable alkylating and halogenating reagents.
Suitable inorganic oxides in the support include talcs, clays SiO2, Al2O3, MgO, ZrO2, TiO2, Fe2O3, B2O3, CaO, ZnO, BaO, ThO2 and mixtures thereof such as silica alumina, silica alumina titania, zeolite, ferrite and glass fibers. Such mixtures include physical and gelled mixtures. In addition, the above-mentioned inorganic oxide carriers may contain a small amount of carbonates, nitrates, sulfates or the like. Additional suitable inorganic oxide materials include aluminum phosphate gel materials and mixtures of two or more of the foregoing.
The transition metal combined with the inorganic or inorganic oxide material describe above, is selected from metals in Groups 3 to 10 of the Periodic Table and preferably in an oxide form of these metals. Most preferred transition metals are oxides from the Groups 3-6 of the Periodic Table. Most preferably are vanadia, zirconia, chromia, and titania and mixtures thereof. The transition metal is from about 0.1 wt. % of the total weight of the support to 100 wt. % of the total weight of the support.
The degree of porosity in the carrier may be any level that is achievable in the starting material. Preferably, the carrier particles of the present invention have a pore volume of at least 0.1 cc/g; preferably from 0.25 to 5 cm3/g; most preferably from about 0.7 to 3.0 cm3/g.
Preferably, the particles have a surface area of about 1-1000 m2/g; preferably from about 25-600 m2/g; more preferably from about 100 to 450 m2/g. The typical median particle size for a suitable co-gel for this invention is from 1 to 300 microns; preferably from 5 to 200 microns; and more preferably from 180 microns.
Pore volume and surface area can be, for example, measured from volume of nitrogen gas adsorbed in accordance with BET method. (Refer to J. Am. chem. Soc., Vol. 60, p. 309 (1983)).
The metal containing support is preferably calcined prior to treatment with the alkylating and halogenating reagents at a temperature in the range of from about 150xc2x0 C. to 1000xc2x0 C., for a time of from 1 minute to 24 hours; preferably in the range of about 150xc2x0 C. to 800xc2x0 C., for a time of from 1 minute to 6 hours; and more preferably in the range of about 300xc2x0 C. to 500xc2x0 C., for a time of from 2 to 6 hours.
The Alkylating Reagent
The alkylating reagent is represented by the formula MaRa wherein M is a metal from Group 1, 2 and 13 from the Periodic Table and mixtures thereof and where a is the valence state of the metal; preferably Mg, Zn, Li, Al, Na, and K and mixtures thereof; most preferably Mg, Zn, Al and mixtures thereof.
The R""s are the same or independent and are radicals selected from the group consisting of halogens, alkyls, aryls, alkylaryls, arylalkyls, alkoxys and alkenyls, cyclopentadienyl with from 0 to 5 substituents, wherein the substituents may form rings (i.e., indenyl) compounds and mixtures thereof; and wherein at least one R is an alkyl, alkyaryl, arylalkyl or cyclopentadienyl. The number of R""s is sufficient to balance the valence state a of the metal.
Preferred are radicals of chlorine, bromine; C1-20 alkenyls (preferably, ethenyl, propylenyl, butenyl, and pentenyl); C1-20 alkyl group (preferably, methyl, ethyl, n-propyl, iso-propyl, n-butyl, n-octyl, and 2-ethylhexyl groups); C1-C20 alkoxys (preferably, ethoxy, propoxy, butoxy); C6-20 aryl groups, alkylaryl groups, (preferably, phenyl, p-tolyl, benzyl, 4-t-butylphenyl, 2,6 dimethylphenyl, 3,5-methylphenyl, 2,4-dimethylphenyl, 2,3-dimethylphenyl groups); C5-C25 cyclopentadienyls (preferably, mono and bis cyclopentadienyl) and mixtures of two or more of the foregoing.
The most preferred alkylating reagents are hydrocarbon soluble dialkylmagnesium compounds, such as dialkylmagnesium, alkylmagnesium alkoxide, alkylmagnesium halide, as well as dialkylzinc, trialkylaluminum and mixtures thereof. Specific examples of the most preferred alkylating agents are diethylzinc, dibutylmagnesium, triethylaluminum, butylethylmagnesium, dibutylmagnesium, butylmagnesium butoxide, butylethylmagnesium butoxide and ethylmagnesium chloride.
The amount of the alkylating agent used in the present invention is measured in mmole of metal in the alkylating agent to gram of transition metal containing support. Preferably, the ratio of these reagents is at least 0.1 mmole of alkylating agent per one gram of support; preferably the ratio is from about 1 mmole/gram to 5 mmole/gram; and most preferably, the ratio is from about 2 mmole/gram to 3 mmole/gram.
The Halogenating Reagent
The halogenating reagent used in the present invention is represented by the formula RmXn wherein X is a monovalent radical selected from among the halogens or mixtures thereof; preferably chlorine, fluorine, bromine and mixtures thereof. The R is a radical that is selected from the group consisting of H and hydrocarbon radicals selected from the group consisting of C7-20 alkylaryls (such as benzyl and 4-methylbenzyl); C1-C20 alkyl, preferably, C1-C10 alkyls; and more preferably methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, n-octyl, and 2-ethylhexyl groups; and other radicals selected from the group consisting of boron; organic acids, preferably benzyl acids and acetic acids, most preferably phthalic acid; phosphorus; thionyl; sulfuryl; carbonyl, preferably phosgenes; nitrosyl; silicon; alkylsilicon; aluminum; alkylaluminum; ammonium silicates and mixtures thereof, wherein m is the valence of R and m=n. Furthermore, R can be zero, e.g., where the halogenating agent is chlorine or bromine.
Preferred halogenating agents are diethyl-aluminumchloride, trimethylchlorosilane, t-butylchloride, boron trichloride, aluminum trichloride, ammonium hexafluororsilicate, thionyl chloride, sulfuryl chloride, phosgene, nitrosyl chloride, chlorine, bromine, silicon chloride and mixtures thereof; most preferred are chlorinating agents, with BCl3 and trimethylchlorosilane and mixtures thereof being even more preferred.
The halogenating reagent should be used in a quantity that provides halogens in an amount of from about 2 to 10 times the molar amount of the alkylating reagent present in the support. The most preferred amount is from about 4 to about 8 times the amount of alkylating reagent; and the even more preferred is approximately 6 times.
Method of the Catalyst Composition
The method of producing the catalyst according to the present invention comprises the steps:
1) combining the support as described containing a Group 3-10 transitional metal, with an alkylating reagent as herein defined, in dry degassed solvents such as ethers, aromatics, aliphatics and mixtures thereof; preferably in non-coordinating, aliphatic solvents, preferably C5-C8 solvents, such as heptanes, pentanes, and hexane;
2) combining the reaction product of step 1) with a halogenating reagent as defined above.
The combining of these ingredients is carried at temperatures ranging from xe2x88x9230xc2x0 C. to the boiling point of the solvent used, preferably from about 0xc2x0 C. to about 130xc2x0 C., and most preferably between room temperature and about 50xc2x0 C. Some halogenating reagents may require temperature above room temperature to form the desired catalyst.
Method of Using the Catalyst Compositions
Activation of the supported catalysts or catalytic systems of the present invention may be accomplished by any suitable method for bringing the support and/or the supported catalyst into contact with an appropriate catalytic activator, such as an organoaluminum compound, to create the active catalytic species. Such mixing techniques include the mixing of the dry powders, through gaseous impregnation or via a slurry composition in a solvent.
The catalytic activator includes those represented by the formula R4nAlX3xe2x88x92n where R4 is a hydrocarbon radical having from 1 to about 20 carbon atoms, X is monovalent radical selected from the halogens and hydrogen, and n is an integer of 0-3. Examples of specific compounds include trimethylaluminum, triisobutylaluminum, tridodecylaluminum, tricyclohexyaluminum, triphenylaluminum, tribenzylaluminum, diethylaluminum chloride, ethylaluminum dichloride, isopropylaluminum dibromide, diisobutylaluminum hydride, and the like, and mixtures thereof.
The catalytic activator also includes alumoxanes such as methylaluminoxane, isobutylaluminoxane.
The activated catalyst is useful to polymerize olefinic materials, particularly ethylene. Polmerizations of olefinic monomers can be accomplished by any number of well known techniques by having the olefinic material come into contact with the polymerization catalyst(s) in a reaction zone under appropriate conditions.
As used herein, xe2x80x9cPolymerizationxe2x80x9d includes copolymerization and terpolymerization and the terms olefins and olefinic monomer includes olefins, alpha-olefins, diolefins, strained cyclic olefins, styrenic monomers, acetylenically unsaturated monomers, cyclic olefins alone or in combination with other unsaturated monomers. While the catalyst system of the present invention is active for this broad range of olefinic monomer feedstock, alpha-olefin polymerizations is preferred, especially the homopolymerization of ethylene and propylene or the copolymerization of ethylene with olefins having 3 to 10 carbon atoms.
xe2x80x9cPolymerization techniquesxe2x80x9d for olefin polymerization according to the present invention can be solution polymerization, slurry polymerization or gas phase polymerization techniques. Method and apparatus for effecting such polymerization reactions are well known and described in, for example, Encyclopedia of Polymer Science and Engineering published by John Wiley and Sons, 1987, Volume 7, pages 480-488 and 1988, Volume 12, pages 504-541. The catalyst according to the present invention can be used in similar amounts and under similar conditions to known olefin polymerization catalyst.
Typically, for the slurry process, the temperature is from approximately 0 degrees C. to just below the temperature at which the polymer becomes soluble in the polymerization medium. For the gas phase process, the temperature is from approximately 0 degrees C. to just below the melting point of the polymer. For the solution process, the temperature is typically the temperature from which the polymer is soluble in the reaction medium up to approximately 275 degrees C.
The pressure used can be selected from a relatively wide range of suitable pressures, e.g., from subatmospheric to about 350 Mpa. Suitably, the pressure is from atmospheric to about 6.9 Mpa, or 0.05-10 MPa, especially 0.14-5.5 Mpa. In the slurry or particle form process, the process is suitably performed with a liquid inert diluent such as a saturated aliphatic hydrocarbon. Suitably the hydrocarbon is a C4 to C10 hydrocarbon, e.g., isobutane, heptane or an aromatic hydrocarbon liquid such as benzene, toluene or xylene. The polymer is recovered directly from the gas phase process or by filtration or evaporation from the slurry process or evaporation from the solution process.
The catalyst of the present invention are particularly suited for the gas phase or slurry process.
The compositions according to the present invention are used in a amounts sufficient to cause polymerization in the feedstocks. Typically, the amount used will be in the range of 0.0005 mmole to 10 mmole/liter of reactor; most preferably from 0.01 mmole to 2.5 mmole/liter of reactor.
In addition to the examples of the present invention provided in the examples and in the samples in Tables I-IV below, preferred catalyst can be prepared from the following starting materials.